In recent years, with the development of technology, the function of electronic devices is upgraded continuously. Therefore, the demand for the energy and rate capability properties of lithium battery is increasing. High energy lithium battery has become a research focus in the battery industry.
Lithium battery is classified into primary lithium battery (primary battery) and lithium-ion battery (secondary battery). Relatively, the lithium primary battery has a higher energy density, mainly because the used lithium metal negative electrode has a higher theoretical capacity per gram compared with the carbon-based negative electrode used in the lithium-ion battery. Specifically, the theoretical capacity per gram of the lithium metal negative electrode is 3860 mAh/g, while the theoretical capacity per gram of the carbon-based negative electrode is 372 mAh/g. In addition, there will occur a side reaction in the positive/negative electrode material of the lithium-ion battery during charging and discharging, leading to the generation of an irreversible capacity. Furthermore, during the first charging of a lithium-ion battery, the carbon-based negative electrode will react with electrolyte at the solid-liquid interface and a solid electrolyte interface film (SEI layer) will be formed. This procedure will lead to the loss of part of positive electrode capacity. Based on the above two points, the capacity utilization rate of a conventional lithium-ion battery material is about 90%. In addition, the lithium-ion battery has a higher self-discharge rate while the lithium primary battery has a lower one; the defect of the lithium primary battery is its output power is lower compared with the lithium-ion battery. This is mainly because the lithium primary battery is generally obtained in two ways: one is to increase energy density by increasing the conductivity of the electrode itself, while this is not feasible for the lithium primary battery; the other is to make the electrode to be very thin, however, since metal lithium itself has a low tension strength, the thin lithium plate tends to break during the battery preparation process. In contrary, the negative electrode of lithium-ion battery is made using carbon-based material which itself has a high conductivity capacity to coat on a current collector (e.g. copper foil), thereby the thickness of the electrode plate is controllable to meet the requirement of power.
Based on the description above, the current research on lithium battery is mainly focused on improving the energy density of primary battery and increasing the energy density of the chargeable lithium-ion battery. There are two ways to increase the tension strength of the metal lithium cathode for the primary lithium battery with high power: one way is to increase the mechanical strength by increasing the thickness of the metal lithium in the negative electrode and the other is to increase its mechanical tension strength by adding metal lithium to a thin conductive support component such as metal mesh or metal tape in the manner of spraying or compression.
The first way significantly reduces the utilized portion of the lithium metal negative electrode and lowers the energy density of the battery; furthermore, the lithium metal negative electrode is larger than necessary, which creates a huge potential safety hazard. In the second way, the operation of spraying and compression has to be done in a dry area or an atmosphere that is inert to lithium metal, such as nitrogen or argon. Therefore, the cost of the preparation is high, the preparation procedure becomes complicated, and it is hard to achieve a continual production and to guarantee the uniformity of the negative electrode plate.
One direction of high energy lithium-ion battery research is to develop lithium-ion battery negative electrode materials with high-capacity, including nitrides, silicon-based materials, tin-based materials, etc. The size of such negative electrode materials will increase during the charging and discharging because of the embedding of the lithium ions, however, the volume cannot be restored to its original state after the lithium ions are extracted, which result in volume swelling of the battery, chalking of the electrode and loss of electrochemical activity, thus leading to loss of the capacity and a huge potential safety hazard.